There are many situations in which a substance is to be heated or thawed from a first temperature (e.g. below zero degrees Celsius) to a second temperature (e.g. room temperature). Sometimes it is also important that this heating is effected quickly and at very high precision, i.e. uniformly and without overheating any parts of the substance. In such cases, the heating task may become very challenging. Heating frozen blood plasma to a temperature suitable for introduction into the human body is one example of such heating. However, of course, both within and outside the medical field there are numerous other examples of demanding heating tasks.
WO 02/054833 shows an appliance for equalizing an electromagnetic field, which is not generated in a resonant cavity, and wherein a dielectric load being heated contains matters with one or more dielectric constants and loss factors.
WO 2011/145994 discloses another solution for equalizing a warming process wherein a load is heated via an electromagnetic field. Here, the load is surrounded by a field equalizing material. The load and the electromagnetic field are also moved relative to one another in order to enhance the heating process and render it more energy distribution more uniform.
WO 2011/159815 describes a solution according to which a dielectric load is heated from an initial temperature level to a desired final temperature level by using alternating electromagnetic energy from an energy source, which produces a predefined set of spectral components. A cavity contains the dielectric load, and an antenna transmits an electromagnetic field through the dielectric load. Mechanical processing means cause a relative movement between the dielectric load and the at least one antenna, thus varying a spatial relationship between the alternating electromagnetic field and the dielectric load. As a result, the electromagnetic energy is distributed relatively evenly in the dielectric load. Sensor means register a temperature level of the dielectric load; and based thereon an amount of energy is transmitted through the dielectric load.
Consequently, various solutions are known for heating a dielectric load by using an electromagnetic field, and for example surrounding the load by a field equalizing material to enhance the heating process. Nevertheless, there is yet no solution to automatically detect any leakage from the load or the surrounding material during the heating. Leakage of this type not only risks damaging the load as such, however also the heater might be damaged, or at least require significant cleaning due to the substances having escaped from the load and/or the equalizing material.